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Crystals, Volume 9, Issue 11 (November 2019)

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Cover Story (view full-size image) Carbamazepine (CBZ), a widely used antiepileptic, is known to be sensitive to light. [...] Read more.
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Open AccessArticle
Control of Organic Superconducting Field-Effect Transistor by Cooling Rate
Crystals 2019, 9(11), 605; https://doi.org/10.3390/cryst9110605 - 19 Nov 2019
Abstract
A new superconducting field-effect transistor (FET) in the vicinity of bandwidth-controlled Mott transition was developed using molecular strongly correlated system κ-(BEDT-TTF)2Cu[N(CN)2]Br [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene] laminated on CaF2 substrate. This device exhibited significant cooling-rate dependence of resistance below about [...] Read more.
A new superconducting field-effect transistor (FET) in the vicinity of bandwidth-controlled Mott transition was developed using molecular strongly correlated system κ-(BEDT-TTF)2Cu[N(CN)2]Br [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene] laminated on CaF2 substrate. This device exhibited significant cooling-rate dependence of resistance below about 80 K, associated with glass transition of terminal ethylene group of BEDT-TTF molecule, where more rapid cooling through glass transition temperature leads to the decrease in bandwidth. We demonstrated that the FET properties such as ON/OFF ratio and polarity can be controlled by utilizing cooling rate. Our result may give a novel insight into the design of molecule-based functional devices. Full article
(This article belongs to the Special Issue Structure and Properties of Molecular Conductors)
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Open AccessArticle
Evolution of Microstructure, Texture and Topography during Cold Rolling and Recrystallization of Ni–5at.%W Alloy Substrate for Coated Conductors
Crystals 2019, 9(11), 604; https://doi.org/10.3390/cryst9110604 - 18 Nov 2019
Abstract
In this work, the effect of cold rolling and heat treatment upon the microstructure and texture of the surface layer and cross-section of Ni5W alloy substrate was analyzed via the EBSD technique. A typical copper deformation texture was shown by the cold-rolled Ni5W [...] Read more.
In this work, the effect of cold rolling and heat treatment upon the microstructure and texture of the surface layer and cross-section of Ni5W alloy substrate was analyzed via the EBSD technique. A typical copper deformation texture was shown by the cold-rolled Ni5W alloy substrate. The cube-oriented nuclei were attributed to the rolling direction–transverse direction (RD-TD) plane due to the presence of copper and S rolling textures. Typical large-shape cold-rolled microstructure was presented by the RD-ND surface in the cube-oriented area. During the recrystallization process, the cube-oriented grains did not have a nucleation quantity advantage, but they did have an obvious growth advantage compared with other orientation grains. They can form a strong cube texture by absorbing the random orientation and rolling orientation through the migration of large-angle grain boundaries. Full article
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Open AccessCommentary
A Fundamental Reason for the Need of Two Different Semiconductor Technologies for Complementary Thin-Film Transistor Operations
Crystals 2019, 9(11), 603; https://doi.org/10.3390/cryst9110603 - 17 Nov 2019
Abstract
In this short commentary, we discuss a fundamental reason why two different semiconductor technologies are needed for complementary thin-film transistor (TFT) operations. It is mainly related to an energy-level matching between the band edge of the semiconductor and the work-function energy of the [...] Read more.
In this short commentary, we discuss a fundamental reason why two different semiconductor technologies are needed for complementary thin-film transistor (TFT) operations. It is mainly related to an energy-level matching between the band edge of the semiconductor and the work-function energy of the metal, which is used for the source and drain electrodes. The reference energy level is determined by the energy range of work-functions of typical metals for the source and drain electrodes. With the exception of silicon, both the conduction band edge (EC) and valence band edge (EV) of a single organic or inorganic material are unlikely to match the metal work-function energy whose range is typically from −4 to −6 eV. For example, typical inorganic materials, e.g., Zn–O, have the EC of around −4.5 eV (i.e., electron affinity), so the conduction band edge is within the range of the metal work-function energy, suggesting its suitability for n-channel TFTs. On the other hand, p-type inorganic materials, such as Cu–O, have an EV of around −5.5 eV, so the valence band edge is aligned with metal work-function energy, thus the usage for p-channel TFTs. In the case of p-type and n-type organic materials, their highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO) should be aligned with metal work-function energy. For example, p-type organic material, e.g., pentacene, has a HOMO level around −5 eV, which is within the range of the metal work-function energy, implying usage for p-channel TFTs. However, its LUMO level is around −3 eV, not being aligned with the metals’ work-function energy. So it is hard to use pentacene for n-channel TFTs. Along with this, n-type organic materials (e.g., C60) should have HOMO levels within the typical metals’ work-function energy for the usage of n-channel TFT. To support this, we provide a qualitative and comparative study on electronic material properties, such as the electron affinity and band-gap of representative organic and inorganic materials, and the work-function energy of typical metals. Full article
(This article belongs to the Special Issue Advances in Thin Film Materials and Devices)
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Open AccessArticle
Fluorescence Properties and Density Functional Theory Calculation of a Structurally Characterized Heterotetranuclear [ZnII2–SmIII2] 4,4′-Bipy-Salamo-Constructed Complex
Crystals 2019, 9(11), 602; https://doi.org/10.3390/cryst9110602 - 17 Nov 2019
Abstract
A new heterotetranuclear complex, [{Zn(L)Sm(NO3)3}2(4,4′-bipy)]·2CH3OH, was synthesized via an unsymmetrical single salamo-like ligand H2L: 6-methoxy-6′-ethoxy-2,2′-[ethylenedioxybis(azinomethyl)]diphenol, with Zn(OAc)2·2H2O, Sm(NO3)3·6H2O, and [...] Read more.
A new heterotetranuclear complex, [{Zn(L)Sm(NO3)3}2(4,4′-bipy)]·2CH3OH, was synthesized via an unsymmetrical single salamo-like ligand H2L: 6-methoxy-6′-ethoxy-2,2′-[ethylenedioxybis(azinomethyl)]diphenol, with Zn(OAc)2·2H2O, Sm(NO3)3·6H2O, and 4,4′-bipyridine by the one-pot method. The [ZnII2–SmIII2] complex was validated via elemental analysis, powder X-ray diffraction (PXRD) analysis, infrared spectroscopy, and ultraviolet–visible (UV–Vis) absorption spectroscopy. The X-ray single crystal diffraction analysis of the [ZnII2–SmIII2] complex was carried out via X-ray single-crystal crystallography. The crystal structure and supramolecular features were discussed. In addition, while studying the fluorescence properties of the [ZnII2–SmIII2] complex, the density functional theory (DFT) calculation of its structure was also performed. Full article
(This article belongs to the Special Issue Fluorescent Complexes)
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Open AccessArticle
Two Interpenetrated Zn(II) Coordination Polymers: Synthesis, Topological Structures, and Property
Crystals 2019, 9(11), 601; https://doi.org/10.3390/cryst9110601 - 17 Nov 2019
Abstract
Two interpenetrated coordination polymers (CPs) {[Zn1(L)(NO2pbda)]n[Zn2(L)(NO2pbda)]n} (1) and [Zn(L)(Brpbda)]n (2) were prepared by reactions of zinc sulfate heptahydrate with N-donor ligands of 1,4-di(1H-imidazol-4-yl)benzene (L) and auxiliary carboxylic acids [...] Read more.
Two interpenetrated coordination polymers (CPs) {[Zn1(L)(NO2pbda)]n[Zn2(L)(NO2pbda)]n} (1) and [Zn(L)(Brpbda)]n (2) were prepared by reactions of zinc sulfate heptahydrate with N-donor ligands of 1,4-di(1H-imidazol-4-yl)benzene (L) and auxiliary carboxylic acids of nitroterephthalic acid (H2NO2pbda) and 2,5-dibromoterephthalic acid (H2Brpbda), respectively. The structures of the CPs were characterized by Fourier-Transform Infrared (IR) spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The coordination polymer 1 has two different (4, 4) sql 2D layer structures based on the [Zn(L)(NO2pbda)] moiety, which results in inclined interpenetration with a 2D + 2D → 3D architecture, while the CP 2 exhibits a 3-fold interpenetrating dmp network. The diffuse reflectance spectra are also investigated for the CPs 1 and 2. Full article
(This article belongs to the Special Issue Crystal Structure and Thermal Studies of Coordination Compounds)
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Open AccessArticle
Size Matters: New Zintl Phase Hydrides of REGa (RE = Y, La, Tm) and RESi (RE = Y, Er, Tm) with Large and Small Cations
Crystals 2019, 9(11), 600; https://doi.org/10.3390/cryst9110600 - 16 Nov 2019
Abstract
Many Zintl phases exhibiting a CrB type structure form hydrides. Systematic studies of AeTtHx (Ae = Ca, Sr, Ba; Tt = Si, Ge, Sn), LnTtHx (Ln = La, Nd; Tt = Si, Ge, Sn), and LnGaH [...] Read more.
Many Zintl phases exhibiting a CrB type structure form hydrides. Systematic studies of AeTtHx (Ae = Ca, Sr, Ba; Tt = Si, Ge, Sn), LnTtHx (Ln = La, Nd; Tt = Si, Ge, Sn), and LnGaHx (Ln = Nd, Gd) showed the vast structural diversity of these systems. Hydrogenation reactions on REGa (RE = Y, La, Tm) and RESi (RE = Y, Er, Tm) were performed in steel autoclaves under hydrogen pressure up to 5 MPa and temperatures up to 773 K. The products were analyzed by X-ray and neutron powder diffraction. RESi (RE = Y, Er, Tm) form hydrides in the C-LaGeD type. LaGaD1.66 is isostructural to NdGaD1.66 and shows similar electronic features. Ga-D distances (1.987(13) Å and 2.396(9) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. In TmGaD0.93(2) with a distorted CrB type structure deuterium atoms exclusively occupy tetrahedral voids. Theoretical calculations on density functional theory (DFT) level confirm experimental results and suggest metallic properties for the hydrides. Full article
(This article belongs to the Section Crystalline Materials)
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Open AccessArticle
Synthesis, Characterization, and Crystal Structure of N-(3-nitrophenyl)cinnamamide
Crystals 2019, 9(11), 599; https://doi.org/10.3390/cryst9110599 - 15 Nov 2019
Abstract
N-(3-nitrophenyl)cinnamamide 1 with formula C15H12N2O3 was synthesized, and its crystal structure was determined by single-crystal X-ray diffraction analysis. Compound 1 crystallizes in the monoclinic space group P21/n with unit cell dimensions: a = 6.7810 (5) [...] Read more.
N-(3-nitrophenyl)cinnamamide 1 with formula C15H12N2O3 was synthesized, and its crystal structure was determined by single-crystal X-ray diffraction analysis. Compound 1 crystallizes in the monoclinic space group P21/n with unit cell dimensions: a = 6.7810 (5) Å, b = 23.0913 (15) Å, c = 8.2079 (5) Å, V = 1282.76 (15) Å3, Z = 4, determined at 150 K with MoKα radiation. The experimental structure refined against atomic scattering factors is compared with the structure obtained using a Hirshfeld Atom Refinement (HAR) approach and Density Functional Theory (DFT) geometry optimizations. Full article
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Open AccessArticle
Symmetry Breaking Induced Pockels Effect in a Tilted Field Switching BPIII Cell
Crystals 2019, 9(11), 598; https://doi.org/10.3390/cryst9110598 - 15 Nov 2019
Abstract
In this study, we propose driving the amorphous blue phase III (BPIII) with a tilted electric field to enhance or magnify its inherent linear electro-optical properties. The electro-optical properties of in-plane-switching (IPS) BPIII and tilted-field-switching (TFS) BPIII cells are compared here. According to [...] Read more.
In this study, we propose driving the amorphous blue phase III (BPIII) with a tilted electric field to enhance or magnify its inherent linear electro-optical properties. The electro-optical properties of in-plane-switching (IPS) BPIII and tilted-field-switching (TFS) BPIII cells are compared here. According to the change in the induced birefringence with varying the strength of the electric field in the TFS-BPIII cell, the Kerr effect occurs in the low electric field and the Pockels effect dominates in the high electric field. In addition, the transmittance of the TFS-BPIII cell depends on the polarity of the applied field from 1 Hz to 10 kHz. It also results in the rise time of the TFS-BPIII cell being almost half of that of the IPS-BPIII cell. These experimental results and discussion allowed us to unravel the mystery of the amorphous BPIII step by step and provide the potential application of BPIII in photonic devices. Full article
(This article belongs to the Special Issue Advances in Blue Phases Liquid Crystals )
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Open AccessReview
Carboxylic Ester Hydrolases in Bacteria: Active Site, Structure, Function and Application
Crystals 2019, 9(11), 597; https://doi.org/10.3390/cryst9110597 - 14 Nov 2019
Abstract
Carboxylic ester hydrolases (CEHs), which catalyze the hydrolysis of carboxylic esters to produce alcohol and acid, are identified in three domains of life. In the Protein Data Bank (PDB), 136 crystal structures of bacterial CEHs (424 PDB codes) from 52 genera and metagenome [...] Read more.
Carboxylic ester hydrolases (CEHs), which catalyze the hydrolysis of carboxylic esters to produce alcohol and acid, are identified in three domains of life. In the Protein Data Bank (PDB), 136 crystal structures of bacterial CEHs (424 PDB codes) from 52 genera and metagenome have been reported. In this review, we categorize these structures based on catalytic machinery, structure and substrate specificity to provide a comprehensive understanding of the bacterial CEHs. CEHs use Ser, Asp or water as a nucleophile to drive diverse catalytic machinery. The α/β/α sandwich architecture is most frequently found in CEHs, but 3-solenoid, β-barrel, up-down bundle, α/β/β/α 4-layer sandwich, 6 or 7 propeller and α/β barrel architectures are also found in these CEHs. Most are substrate-specific to various esters with types of head group and lengths of the acyl chain, but some CEHs exhibit peptidase or lactamase activities. CEHs are widely used in industrial applications, and are the objects of research in structure- or mutation-based protein engineering. Structural studies of CEHs are still necessary for understanding their biological roles, identifying their structure-based functions and structure-based engineering and their potential industrial applications. Full article
(This article belongs to the Special Issue Crystallographic Studies of Enzymes)
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Open AccessArticle
A Newly Synthesized Heterobimetallic NiII-GdIII Salamo-BDC-Based Coordination Polymer: Structural Characterization, DFT Calculation, Fluorescent and Antibacterial Properties
Crystals 2019, 9(11), 596; https://doi.org/10.3390/cryst9110596 - 14 Nov 2019
Abstract
A unprecedented hetero-bimetallic 3d-4f BDC-salamo-based coordination polymer, [(L)Ni(BDC)Gd(NO3)(DMF)] was prepared and validated via elemental analyses, IR and UV–Visible absorption spectra, DFT calculation, and X-ray crystallography. The six-coordinated Ni1 ion lies at the N2O2 donor site of the L [...] Read more.
A unprecedented hetero-bimetallic 3d-4f BDC-salamo-based coordination polymer, [(L)Ni(BDC)Gd(NO3)(DMF)] was prepared and validated via elemental analyses, IR and UV–Visible absorption spectra, DFT calculation, and X-ray crystallography. The six-coordinated Ni1 ion lies at the N2O2 donor site of the L2− moiety, and one DMF O atom and carboxylate O atom occupy, collectively, the axial positions, and form a twisted octahedron. The nine-coordinated Gd1 ion consists of three oxygen atoms (O12, O13, and O14) of two carboxylate groups, two oxygen atoms (O8 and O9) derived from one bidentate nitrate group, and an O2O2 coordination site (O1, O2, O6, and O5) of the L2− unit, forming a twisted three-capped triangular prism coordination geometry. Compared to the ligand (H2L), the fluorescence intensity decreases due to the coordination of metal ions. Meanwhile, the antibacterial activities are researched. Full article
(This article belongs to the Special Issue Fluorescent Complexes)
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Open AccessArticle
Thermal Cyclic Properties of Ti-Pd-Pt-Zr High-Temperature Shape Memory Alloys
Crystals 2019, 9(11), 595; https://doi.org/10.3390/cryst9110595 - 14 Nov 2019
Abstract
In this study, the thermal cyclic properties of Ti-(50−x)Pd-xPt-5Zr alloys (x = 5, 15, 25, at%), comprising B2 and B19 structures in austenite and martensite, were investigated by a thermal cyclic compression test under a constant load of between 15 and 200 MPa. [...] Read more.
In this study, the thermal cyclic properties of Ti-(50−x)Pd-xPt-5Zr alloys (x = 5, 15, 25, at%), comprising B2 and B19 structures in austenite and martensite, were investigated by a thermal cyclic compression test under a constant load of between 15 and 200 MPa. The transformation temperature measured using differential scanning calorimetry increased with increasing Pt concentration. The highest austenite finishing (Af) temperature, 648 °C, was obtained in the Ti-25Pd-25Pt-5Zr alloy. Irrecoverable strain due to thermal cyclic testing was observed during each test, even at a stress of 50 MPa. The work output, calculated as the product of the transformation strain and the applied stress from strain–temperature curves, decreased with increasing Pt concentration. This was because of the lower strength of the austenite phase due to Af increasing with an increase in the concentration of Pt. Although irrecoverable strain was observed with the first thermal cycle test, it decreased after several thermal cyclic tests, which are called training. Full article
(This article belongs to the Special Issue Advanced High Temperature Shape Memory Alloys)
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Open AccessArticle
The Formation and Application of Submicron Spherical BaTiO3 Particles for the Diffusion Layer of Medical Dry Films
Crystals 2019, 9(11), 594; https://doi.org/10.3390/cryst9110594 - 14 Nov 2019
Abstract
Submicron spherical barium titanate (BaTiO3) was prepared by batch precipitation in an alkaline solution of a BaCl2–TiCl4–NaOH reaction system. The influence of various parameters on the morphology of BaTiO3 powders was investigated in this study. Spherical [...] Read more.
Submicron spherical barium titanate (BaTiO3) was prepared by batch precipitation in an alkaline solution of a BaCl2–TiCl4–NaOH reaction system. The influence of various parameters on the morphology of BaTiO3 powders was investigated in this study. Spherical BaTiO3 particles can be obtained by reacting for 20 min, which was used to prepare the dry sheet of a medical dry chemical reagent. The morphology of the particles was affected by the stirring speed and the alkaline concentration; the particle size decreased as the stirring speed increased. The hydroxyl ion in the solution acts as a catalyst that can promote the formation of spherical BaTiO3. The formation mechanism of the BaTiO3 sphere is proposed to have three steps: the formation of a Ba–Ti gel and nucleation, self-combination/growth of the BaTiO3 crystal nucleus, and Ostwald ripening. In addition, it is feasible to apply the prepared BaTiO3 sphere to medical dry chemical detection reagents. Full article
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Open AccessArticle
“Restricted Geometry” Effect on Phase Transitions in KDP, ADP, and CDP Nanocrystals
Crystals 2019, 9(11), 593; https://doi.org/10.3390/cryst9110593 - 14 Nov 2019
Abstract
The dielectric properties of composite materials prepared by the embedding of ferroelectrics potassium dihydrogen phosphate (KDP), cesium dihydrophosphate (CDP), as well as antiferroelectric ammonium dihydrogen phosphate (ADP) into porous glass matrices with an average size of through pores of 7, 46, and 320 [...] Read more.
The dielectric properties of composite materials prepared by the embedding of ferroelectrics potassium dihydrogen phosphate (KDP), cesium dihydrophosphate (CDP), as well as antiferroelectric ammonium dihydrogen phosphate (ADP) into porous glass matrices with an average size of through pores of 7, 46, and 320 nm have been studied. It was found that an increase occurred in the phase transitions temperature (TC) for embedded particles in comparison with corresponding bulk materials. Some possible mechanisms of influence of “restricted geometry” on the Curie temperature are discussed. Estimates of TC shifting as a result of the “pressure effect” caused by elastic stresses in embedded particles as well as the result of bias electric field influence arising due to the piezoelectric effect are made. The possibility of using the tunneling Ising model to explain the experimental results is discussed. Full article
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Open AccessArticle
A Three-Dimensional Cadmium(II) Coordination Network Based on 1,3-Di-(1,2,4-triazole-4-yl)benzene: Synthesis, Structure, and Luminescence Properties
Crystals 2019, 9(11), 592; https://doi.org/10.3390/cryst9110592 - 11 Nov 2019
Abstract
1,2,4-Triazole and its derivatives have been investigated extensively in the construction of coordination polymers. Using a 1,2,4-triazole ligand 1,3-di-(1,2,4-triazole-4-yl)benzene (dtb), a new three-dimensional coordination polymer, {[Cd2(dtb)2(SO4)(H2O)]·(1,2-H2bdc)·SO4}n (1) (1,2-H [...] Read more.
1,2,4-Triazole and its derivatives have been investigated extensively in the construction of coordination polymers. Using a 1,2,4-triazole ligand 1,3-di-(1,2,4-triazole-4-yl)benzene (dtb), a new three-dimensional coordination polymer, {[Cd2(dtb)2(SO4)(H2O)]·(1,2-H2bdc)·SO4}n (1) (1,2-H2bdc = 1,2-benzenedicarboxylic acid), was synthesized under solvothermal conditions. Single-crystal X-ray diffraction analysis revealed that there are two crystallographically different Cd(II) ions in 1 with distorted pentagonal bipyramidal [CdN4O3] geometry and distorted octahedral [CdN4O2] geometry, respectively. The Cd1 atoms are connected by dtb ligands to generate Cd4(dtb)8 secondary building units (SUBs), and the SUBs are further linked by Cd2 atoms into a three-dimensional network with two different one-dimensional channels of 14.63(2) × 14.63(2) and 7.54(2) × 7.54(2) Å2 along the c axis. The topological analysis of the framework has also been discussed. In addition, compound 1 exhibits strong fluorescence emission in the solid state at room temperature. Full article
(This article belongs to the Section Crystalline Materials)
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Open AccessReview
Review of Size Effects during Micropillar Compression Test: Experiments and Atomistic Simulations
Crystals 2019, 9(11), 591; https://doi.org/10.3390/cryst9110591 - 10 Nov 2019
Abstract
The micropillar compression test is a novel experiment to study the mechanical properties of materials at small length scales of micro and nano. The results of the micropillar compression experiments show that the strength of the material depends on the pillar diameter, which [...] Read more.
The micropillar compression test is a novel experiment to study the mechanical properties of materials at small length scales of micro and nano. The results of the micropillar compression experiments show that the strength of the material depends on the pillar diameter, which is commonly termed as size effects. In the current work, first, the experimental observations and theoretical models of size effects during micropillar compression tests are reviewed in the case of crystalline metals. In the next step, the recent computer simulations using molecular dynamics are reviewed as a powerful tool to investigate the micropillar compression experiment and its governing mechanisms of size effects. Full article
(This article belongs to the Special Issue Quantum and Molecular Mechanic Analysis of Crystalline Materials)
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Open AccessArticle
Self-Assembly Motifs of Water in Crystals of Palladium β-Amino Acid Complexes Influenced by Methyl Substitution on the Amino Acid Backbone
Crystals 2019, 9(11), 590; https://doi.org/10.3390/cryst9110590 - 09 Nov 2019
Abstract
Amino acid complexes of transition metals show interesting hydrogen-bonding motifs. In this paper, the syntheses and structures of three β-amino acid complexes of palladium that differ only by the substitution on the β-carbon will be discussed. With only hydrogen on the [...] Read more.
Amino acid complexes of transition metals show interesting hydrogen-bonding motifs. In this paper, the syntheses and structures of three β-amino acid complexes of palladium that differ only by the substitution on the β-carbon will be discussed. With only hydrogen on the β-carbon, no additional water is incorporated into the crystal lattice and hydrogen-bonding is all complex-to-complex. With the addition of one and two methyl groups on the amino acid β-carbon, water is incorporated into the crystal lattice giving intricate water networks held together by complex-to-water and water-to-water hydrogen-bonding networks. Full article
(This article belongs to the Special Issue Novel Hydrogen-bonded Materials with Significant Physical Properties)
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Open AccessArticle
PbI2 Single Crystal Growth and Its Optical Property Study
Crystals 2019, 9(11), 589; https://doi.org/10.3390/cryst9110589 - 09 Nov 2019
Abstract
In this work, we used the chemical vapor transport (CVT) method to grow PbI2 crystals using iodine as a self-transporting agent. The crystals’ structure, composition, and uniformity were confirmed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) measurements. We investigated the [...] Read more.
In this work, we used the chemical vapor transport (CVT) method to grow PbI2 crystals using iodine as a self-transporting agent. The crystals’ structure, composition, and uniformity were confirmed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) measurements. We investigated the band gap energy using absorption spectroscopy measurements. Furthermore, we explored the temperature dependence of the band gap energy, which shifts from 2.346 eV at 300 K to 2.487 eV at 20 K, and extracted the temperature coefficients. A prototype photodetector with a lateral metal–semiconductor–metal (MSM) configuration was fabricated to evaluate its photoelectric properties using a photoconductivity spectrum (PC) and persistent photoconductivity (PPC) experiments. The resonance-like PC peak indicates the excitonic transition in absorption. The photoresponse ILight/IDark-1 is up to 200%. Full article
(This article belongs to the Special Issue Growth and Characterization of Chalcogenide Semiconductors)
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Open AccessArticle
X-ray Assisted Scanning Tunneling Microscopy and Its Applications for Materials Science: The First Results on Cu Doped ZrTe3
Crystals 2019, 9(11), 588; https://doi.org/10.3390/cryst9110588 - 09 Nov 2019
Abstract
Synchrotron X-ray Scanning Tunneling Microscopy (SX-STM) is a novel imaging technique capable of providing real space chemically specific mapping with a potential of reaching atomic resolution. Determination of chemical composition along with ultra-high resolution imaging by SX-STM can be realized through excitation of [...] Read more.
Synchrotron X-ray Scanning Tunneling Microscopy (SX-STM) is a novel imaging technique capable of providing real space chemically specific mapping with a potential of reaching atomic resolution. Determination of chemical composition along with ultra-high resolution imaging by SX-STM can be realized through excitation of core electrons by incident X-rays when their energy is tuned to an absorption edge of a particular atom during raster scanning, as is done in the conventional STM experiments. In this work, we provide a brief summary and the current status of SX-STM and discuss its applications for material science. In particular, we discuss instrumentation challenges associated with the SX-STM technique and present early experiments on Cu doped ZrTe3 single crystals. Full article
(This article belongs to the Special Issue Synchrotron Radiation in Crystallography)
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Open AccessArticle
Bridgman Growth of New Nonlinear Optical Crystal (La1 − xSmx)3Ga5.5Nb0.5O14 for Quasi-Parametric Chirped Pulse Amplification
Crystals 2019, 9(11), 587; https://doi.org/10.3390/cryst9110587 - 09 Nov 2019
Abstract
Samarium-doped La3Nb0.5Ga5.5O14 (Sm:LGN) crystals were grown along a (100)-orientation by the Bridgman method for quasi-parametric chirped pulse amplification (QPCPA) applications. The structure of La1-xSxmGN (x = 0.1, 0.2) crystals was the same [...] Read more.
Samarium-doped La3Nb0.5Ga5.5O14 (Sm:LGN) crystals were grown along a (100)-orientation by the Bridgman method for quasi-parametric chirped pulse amplification (QPCPA) applications. The structure of La1-xSxmGN (x = 0.1, 0.2) crystals was the same as that of La3Nb0.5Ga5.5O14 (LGN) crystals. The effective segregation coefficient of Sm3+ in the La0.9Sm0.1GN crystal was 0.140. The full width at half maximum (FWHM) of La1-xSxmGN (x = 0.1,0.2) crystals was lower than 50″, which indicated the high quality of the crystals. The density of the La0.9Sm0.1GN crystal was 5.968 g/cm3 and that of the La0.8Sm0.2GNcrystal was 5.988 g/cm3. The transmittance of the crystals at 532nm and 800nm was all above 73%. The absorption spectra indicated that the crystals had strong absorption peaks at wavelengths of 1544 and 1595 nm. The thermal properties of La1-xSxmGN (x = 0.1, 0.2) crystals were similar to those of the LGN crystals. The laser damage thresholds of La0.9Sm0.1GN and La0.8Sm0.2GN crystals were, respectively, 188.30 and 54.84 TW/cm2 (@800 nm,35 fs). Full article
(This article belongs to the Special Issue Nonlinear Optics in Crystals and Fibers with Ultra-Fast Laser)
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Open AccessArticle
Effect of ECAP on the Microstructure and Mechanical Properties of a Rolled Mg-2Y-0.6Nd-0.6Zr Magnesium Alloy
Crystals 2019, 9(11), 586; https://doi.org/10.3390/cryst9110586 - 08 Nov 2019
Abstract
A fine-grained Mg-2Y-0.6Nd-0.6Zr alloy was processed by bar-rolling and equal-channel angular pressing (ECAP). The effect of ECAP on the microstructure and mechanical properties of rolled Mg-2Y-0.6Nd-0.6Zr alloy was investigated by optical microscopy, scanning electron microscopy, electron backscattered diffraction and a room temperature tensile [...] Read more.
A fine-grained Mg-2Y-0.6Nd-0.6Zr alloy was processed by bar-rolling and equal-channel angular pressing (ECAP). The effect of ECAP on the microstructure and mechanical properties of rolled Mg-2Y-0.6Nd-0.6Zr alloy was investigated by optical microscopy, scanning electron microscopy, electron backscattered diffraction and a room temperature tensile test. The results show that the Mg-2Y-0.6Nd-0.6Zr alloy obtained high strength and poor plasticity after rolling. As the number of ECAP passes increased, the grain size of the alloy gradually reduced and the texture of the basal plane gradually weakened. The ultimate tensile strength of the alloy first increased and then decreased, the yield strength gradually decreased, and the plasticity continuously increased. After four passes of ECAP, the average grain size decreased from 11.2 µm to 1.87 µm, and the alloy obtained excellent comprehensive mechanical properties. Its strength was slightly reduced compared to the as-rolled alloy, but the plasticity was greatly increased. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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Open AccessArticle
Spatial Beam Filtering with Autocloned Photonic Crystals
Crystals 2019, 9(11), 585; https://doi.org/10.3390/cryst9110585 - 08 Nov 2019
Abstract
We have been numerically demonstrated the mechanism of spatial beam filtering with autocloned photonic crystals. The spatial filtering through different configurations of the multilayered structures based on a harmonically modulated substrate profile is considered. The paper demonstrates a series of parameter studies to [...] Read more.
We have been numerically demonstrated the mechanism of spatial beam filtering with autocloned photonic crystals. The spatial filtering through different configurations of the multilayered structures based on a harmonically modulated substrate profile is considered. The paper demonstrates a series of parameter studies to look for the best spatial beam filtering performance. The optimization results show that a beam spectral width of 39.2° can be reduced to that of 5.92°, leading to high potential applications for integrated optical microsystems. Full article
(This article belongs to the Special Issue Sonic and Photonic Crystals)
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Open AccessReview
Interaction of Dislocations and Interfaces in Crystalline Heterostructures: A Review of Atomistic Studies
Crystals 2019, 9(11), 584; https://doi.org/10.3390/cryst9110584 - 07 Nov 2019
Abstract
Interfaces in heterostructures of crystalline materials could strongly affect the slip of dislocations. Such interfaces have become one of the most popular methods to tailor material strength and ductility. This review focuses on the interaction of dislocations and interfaces in heterostructures, in which [...] Read more.
Interfaces in heterostructures of crystalline materials could strongly affect the slip of dislocations. Such interfaces have become one of the most popular methods to tailor material strength and ductility. This review focuses on the interaction of dislocations and interfaces in heterostructures, in which at least one component is metallic, as investigated by molecular dynamics, in order to systematically summarize our understanding about how dislocations interact with the interfaces. All the possible heterostructures of metallic materials are covered, such as twin boundaries, grain boundaries, bi-metal interfaces and metal/non-metal interfaces. Dislocations may either penetrate the interfaces by inducing steps into the interfaces or dissociate within the interfaces, depending on the type and orientation of the interface as well as the applied strain. Related dislocation interactions at the interface are also presented. In addition, we also discuss the effect of dislocation types, of applied strain and of the deformation method on the interaction of dislocations and interfaces. Full article
(This article belongs to the Special Issue Dislocations in Heterostructures)
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Open AccessArticle
Molecular–Statistical Theory for the Description of Re-Entrant Ferroelectric Phase
Crystals 2019, 9(11), 583; https://doi.org/10.3390/cryst9110583 - 07 Nov 2019
Abstract
The re-entrant ferroelectric phase (Sm- C re * ) is investigated in the framework of a molecular–statistical approach. It was found that anticlinic synpolar along the smectic layer normal phase can arise below the antiferroelectric phase (Sm- C A * ) in the [...] Read more.
The re-entrant ferroelectric phase (Sm- C re * ) is investigated in the framework of a molecular–statistical approach. It was found that anticlinic synpolar along the smectic layer normal phase can arise below the antiferroelectric phase (Sm- C A * ) in the temperature scale, and we suggest this phase to be Sm- C re * . We have shown that in the vicinity of Sm- C A * –Sm- C re * phase transition temperature, a very small electric field can cause a transition into the bidomain synclinic phase, where the helical pitch is unwound and the tilt planes have contributions either along or against the electric field. The helical rotation, elasticity and deformation of the Sm- C * , Sm- C A * and Sm- C re * structures without electric field or in the presence of electric field, as well as the dielectric response, are investigated. It is shown that Sm- C re * can arise solely due to the dipole–dipole interaction, and thus, in contrast to the conventional (improper) ferroelectric Sm- C * , appears to be the proper ferroelectric phase. Full article
(This article belongs to the Special Issue Ferroelectric and Ferromagnetic Liquid Crystals)
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Open AccessArticle
Avalanches in Compressed Sandstone: Crackling Noise under Confinement
Crystals 2019, 9(11), 582; https://doi.org/10.3390/cryst9110582 - 07 Nov 2019
Abstract
The acoustic emission, AE, from avalanches of local cracks and microstructural changes of sandstone under confined compression have been reported. These avalanches soften the underlying minerals and play a key role as indicators for the prediction of geo-engineering disasters, such as mining collapses, [...] Read more.
The acoustic emission, AE, from avalanches of local cracks and microstructural changes of sandstone under confined compression have been reported. These avalanches soften the underlying minerals and play a key role as indicators for the prediction of geo-engineering disasters, such as mining collapses, rock outbursts caused by high ground stress, and man-made quakes by fracking. Compressed sandstone is a model material for the investigation of avalanches. The avalanche energies, amplitudes, and waiting times show the probability distributions that allow us to distinguish between three compression stages; namely, (I) pre-failure, (II) correlated failure, and (III) post-failure. The energy of stage I and stage II is power-law distributed and scale invariant, while post-failure experiments show power laws with high exponential damping (friction). The scaling behavior is close to the predictions of a mean-field (MF) model (stage II) and a force-integrated mean-field model (stage I). Confinement shifts the value of the energy exponent closer to the MF prediction. Omori’s law and waiting time distributions are independent of stress during the compression; their scaling exponents are very similar to those found in seismological studies. Full article
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Open AccessCommunication
Naked Metal Cations Swimming in Protein Crystals
Crystals 2019, 9(11), 581; https://doi.org/10.3390/cryst9110581 - 07 Nov 2019
Abstract
The presence of isolated metal cations, far from any other atom, is not uncommon in protein crystal structures. A systematic survey of the Protein Data Bank showed that nearly 8% of the metal cations are naked, more frequently if they can interact only [...] Read more.
The presence of isolated metal cations, far from any other atom, is not uncommon in protein crystal structures. A systematic survey of the Protein Data Bank showed that nearly 8% of the metal cations are naked, more frequently if they can interact only electrostatically with their neighbors. Surprisingly, this seemed to be only weakly related to the crystallographic resolution. Full article
(This article belongs to the Section Biomolecular Crystals)
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Open AccessArticle
Electronic Structure of Oxygen-Deficient SrTiO3 and Sr2TiO4
Crystals 2019, 9(11), 580; https://doi.org/10.3390/cryst9110580 - 07 Nov 2019
Abstract
The conductive behavior of the perovskite SrTiO 3 is strongly influenced by the presence of oxygen vacancies in this material, therefore the identification of such defects with spectroscopic methods is of high importance. We use density functional theory to characterize the defect-induced states [...] Read more.
The conductive behavior of the perovskite SrTiO 3 is strongly influenced by the presence of oxygen vacancies in this material, therefore the identification of such defects with spectroscopic methods is of high importance. We use density functional theory to characterize the defect-induced states in SrTiO 3 and Sr 2 TiO 4 . Their signatures at the surface, the visibility for scanning tunneling spectroscopy and locally conductive atomic force microscopy, and the core-level shifts observed on Ti atoms in the vicinity of the defect are studied. In particular, we find that the exact location of the defect state (e.g., in SrO or TiO 2 planes relative to the surface) are decisive for their visibility for scanning-probe methods. Moreover, the usual distinction between Ti 3 + and Ti 2 + species, which can occur near defects or their aggregates, cannot be directly translated in characteristic shifts of the core levels. The width of the defect-induced in-gap states is found to depend critically on the arrangement of the defects. This also has consequences for the spectroscopic signatures observed in so-called resistive switching phenomena. Full article
(This article belongs to the Special Issue Electronic Phenomena of Transition Metal Oxides)
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Open AccessArticle
Graphene Adhesion Mechanics on Iron Substrates: Insight from Molecular Dynamic Simulations
Crystals 2019, 9(11), 579; https://doi.org/10.3390/cryst9110579 - 06 Nov 2019
Abstract
The adhesion feature of graphene on metal substrates is important in graphene synthesis, transfer and applications, as well as for graphene-reinforced metal matrix composites. We investigate the adhesion energy of graphene nanosheets (GNs) on iron substrate using molecular dynamic (MD) simulations. Two Fe–C [...] Read more.
The adhesion feature of graphene on metal substrates is important in graphene synthesis, transfer and applications, as well as for graphene-reinforced metal matrix composites. We investigate the adhesion energy of graphene nanosheets (GNs) on iron substrate using molecular dynamic (MD) simulations. Two Fe–C potentials are examined as Lennard–Jones (LJ) pair potential and embedded-atom method (EAM) potential. For LJ potential, the adhesion energies of monolayer GN are 0.47, 0.62, 0.70 and 0.74 J/m2 on the iron {110}, {111}, {112} and {100} surfaces, respectively, compared to the values of 26.83, 24.87, 25.13 and 25.01 J/m2 from EAM potential. When the number of GN layers increases from one to three, the adhesion energy from EAM potential increases. Such a trend is not captured by LJ potential. The iron {110} surface is the most adhesive surface for monolayer, bilayer and trilayer GNs from EAM potential. The results suggest that the LJ potential describes a weak bond of Fe–C, opposed to a hybrid chemical and strong bond from EAM potential. The average vertical distances between monolayer GN and four iron surfaces are 2.0–2.2 Å from LJ potential and 1.3–1.4 Å from EAM potential. These separations are nearly unchanged with an increasing number of layers. The ABA-stacked GN is likely to form on lower-index {110} and {100} surfaces, while the ABC-stacked GN is preferred on higher-index {111} surface. Our insights of the graphene adhesion mechanics might be beneficial in graphene growing, surface engineering and enhancement of iron using graphene sheets. Full article
(This article belongs to the Special Issue Graphene Mechanics)
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Open AccessArticle
Synthesis and Simulation of CaF2@Al(OH)3 Core-Shell Coated Solid Lubricant Composite Powder
Crystals 2019, 9(11), 578; https://doi.org/10.3390/cryst9110578 - 06 Nov 2019
Abstract
In self-lubricating ceramic tools, adding CaF2 will significantly reduce the mechanical properties of ceramic tools. Based on heterogeneous nucleation theory, we have recently prepared aluminum hydroxide (Al(OH)3) coating on calcium fluoride (CaF2) through a liquid-phase heterogeneous nucleation method. [...] Read more.
In self-lubricating ceramic tools, adding CaF2 will significantly reduce the mechanical properties of ceramic tools. Based on heterogeneous nucleation theory, we have recently prepared aluminum hydroxide (Al(OH)3) coating on calcium fluoride (CaF2) through a liquid-phase heterogeneous nucleation method. By adding CaF2@Al(OH)3 coated powder to replace CaF2 powder, the self-lubricating ceramic tools maintain higher lubricity while also having better mechanical properties. The coating process was further confirmed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, we used the molecular simulation software to simulate the suspension system of CaF2, Al(NO3)3·9H2O, and Al(OH)3 to study the process of Al(OH)3 coating on the surface of CaF2 particle to form CaF2@Al(OH)3 powders with core-shell structure. Further, the formation and evolution of Al(OH)3 molecules on the surface of CaF2 were analyzed. Full article
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Open AccessArticle
Crystal Structures of the 43 kDa ATPase Domain of Xanthomonas Oryzae pv. Oryzae Topoisomerase IV ParE Subunit and its Complex with Novobiocin
Crystals 2019, 9(11), 577; https://doi.org/10.3390/cryst9110577 - 05 Nov 2019
Abstract
Topoisomerase IV, one of the best-established antibacterial targets, is an enzyme crucial for chromosome segregation and cell division by catalyzing changes in DNA topology through breaking and rejoining DNA. This enzyme functions as a heterotetramer consisting of two ParC and two ParE subunits. [...] Read more.
Topoisomerase IV, one of the best-established antibacterial targets, is an enzyme crucial for chromosome segregation and cell division by catalyzing changes in DNA topology through breaking and rejoining DNA. This enzyme functions as a heterotetramer consisting of two ParC and two ParE subunits. Aminocoumarin class inhibitors target the ParE subunit, while widely used quinolones target the ParC subunit. Here, we determined the crystal structure of the ParE 43 kDa ATPase domain from Xanthomonas oryzae pv. oryzae. Size exclusion chromatography showed that the ParE ATPase domain exists as a monomer in solution, while it dimerizes when ATP is added. Structural comparison with the structure of Escherichia coli ParE in complex with an ATP analogue showed large conformational change of the subdomains within the protein. We also determined the structure of the ParE ATPase domain in complex with novobiocin, a natural product aminocoumarin class inhibitor, revealing its binding mode and the structural change within the ATP-binding site induced by novobiocin binding. These results could provide a basis for the design of more potent topoisomerase IV inhibitors with improved antibacterial activity. Full article
(This article belongs to the Special Issue Crystallographic Studies of Enzymes)
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Open AccessArticle
Quantitative Analysis of Photon Density of States for One-Dimensional Photonic Crystals in a Rectangular Waveguide
Crystals 2019, 9(11), 576; https://doi.org/10.3390/cryst9110576 - 04 Nov 2019
Abstract
Light propagation in one-dimensional (1D) photonic crystals (PCs) enclosed in a rectangular waveguide is investigated in order to achieve a complete photonic band gap (PBG) while avoiding the difficulty in fabricating 3D PCs. This work complements our two previous articles (Phys. Rev. E) [...] Read more.
Light propagation in one-dimensional (1D) photonic crystals (PCs) enclosed in a rectangular waveguide is investigated in order to achieve a complete photonic band gap (PBG) while avoiding the difficulty in fabricating 3D PCs. This work complements our two previous articles (Phys. Rev. E) that quantitatively analyzed omnidirectional light propagation in 1D and 2D PCs, respectively, both showing that a complete PBG cannot exist if an evanescent wave propagation is involved. Here, we present a quantitative analysis of the transmission functions, the band structures, and the photon density of states (PDOS) for both the transverse electric (TE) and transverse magnetic (TM) polarization modes of the periodic multilayer heterostructure confined in a rectangular waveguide. The PDOS of the quasi-1D photonic crystal for both the TE and TM modes are obtained, respectively. It is demonstrated that a “complete PBG” can be obtained for some frequency ranges and categorized into three types: (1) below the cutoff frequency of the fundamental TE mode, (2) within the PBG of the fundamental TE mode but below the cutoff frequency of the next higher order mode, and (3) within an overlap of the PBGs of either TE modes, TM modes, or both. These results are of general importance and relevance to the dipole radiation or spontaneous emission by an atom in quasi-1D periodic structures and may have applications in future photonic quantum technologies. Full article
(This article belongs to the Special Issue Sonic and Photonic Crystals)
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